1. Field of the Invention
The present invention relates to an air conditioning system for a vehicle, particularly an air conditioning system which changes air introduced from outside (hereinafter referred to as the outside-air mode) to air inside a vehicle compartment (hereinafter referred to as the inside-air mode) when the outside air is polluted or noxious.
2. Description of the Related Art
Air conditioning systems disclosed in JP-B2-64-3687 and JP-B2-47-36974 are provided with a gas sensor which detects polluted air and a control unit which controls an air switching door. When the outside air is polluted to a certain extent, the control unit drives the air switching door to change the outside-air mode to the inside-air mode.
When an automobile vehicle (hereinafter referred to the front vehicle) is running in front of our vehicle, the gas sensor detects the exhaust gases emitted by the front vehicle--which is much more than the exhaust gases emitted while the engine is idling--so that the control unit selects the inside air mode. If the front vehicle stops at the red traffic light with the engine being idling, the exhaust gases is reduced so that the inside air mode is changed to the outside air mode by the control unit. However, the driver is apt to feel that the outside air is still polluted by the front vehicle, and wants to change the outside air mode to the inside air mode. Thus, operation of the control unit makes the driver uncomfortable.